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A374155
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a(n) is the least prime that is a quadratic residue modulo prime(n). First column of A373751.
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1
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2, 3, 5, 2, 3, 3, 2, 5, 2, 5, 2, 3, 2, 11, 2, 7, 3, 3, 17, 2, 2, 2, 3, 2, 2, 5, 2, 3, 3, 2, 2, 3, 2, 5, 5, 2, 3, 41, 2, 13, 3, 3, 2, 2, 7, 2, 5, 2, 3, 3, 2, 2, 2, 3, 2, 2, 5, 2, 3, 2, 7, 17, 7, 2, 2, 7, 5, 2, 3, 3, 2, 2, 2, 3, 5, 2, 5, 3, 2, 2, 3, 3, 2, 2, 2
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OFFSET
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1,1
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LINKS
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EXAMPLE
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a(38) = 41 because row 38 of A373751 starts 41, 43, 47, ..., which are the primes that are quadratic residues modulo 163.
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MAPLE
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a := proc(n) local a, p; a := 1; p := ithprime(n); while true do a := a + 1;
if NumberTheory:-QuadraticResidue(a, p) = 1 and isprime(a) then return a fi od end: seq(a(n), n = 1..85);
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PROG
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(PARI) a(n) = my(p=prime(n), q=2); while (!issquare(Mod(q, p)), q=nextprime(q+1)); q; \\ Michel Marcus, Jun 29 2024
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CROSSREFS
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Variant: A306530 (differs in the first 3 values).
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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